There are two types of anger on highest level. In Sanskrit, it is called Krodha.
1. Anger comes which debases the mind: The root of this anger is pride, which makes one angry when slighted. This prevents the mind from seeing things in perspective and makes one’s judgment defective.
2. Anger which leads to spiritual growth : Yogi is angry with himself when his mind stoops low or when all his learning and experience fail to stop him from folly. He stern with himself when he deals with his own faults, but gentle with faults of others.
Gentleness of mind is attribute of a Yogi, whose heart melts at all suffering. In him gentleness for others and firmness for himself go hand in hand, and in his presence all hostilities are given up.
Source: Book – Light on Yoga